DEVELOPMENT OF FUNDAMENTAL EQUATIONS G(P,T) AND BACKWARD EQUATIONS T(P,H) AND T(P,S) FOR THE NEW INDUSTRIAL FORMULATION

This paper describes equations for a New Industrial Formulation (NIF) designed to replace the current industrial formulation IFC-67. The basic equations for NIF are two fundamental equations in the form of the Gibbs energy g(p,T) for the liquid and the gas region of H²O. Preliminary g equations for both regions are presented. Additionally, preliminary so-called backward equations T(p,h) and T(p,s) for the liquid region have been developed. The equations presented meet the IAPWS requirements regarding accuracy and numerical consistency. The calculation speed of the new set of equations is, in general, about three times faster than for the IFC-67 functions. For the gas region, the development of the backward equations has not yet been finished.